Serial.available() have a issue, its not able to return availiable bytes

[The3ven]

Basic Infos

• [X] This issue complies with the issue POLICY doc.
• [X] I have read the documentation at readthedocs and the issue is not addressed there.
• [ ] I have tested that the issue is present in current master branch (aka latest git).
• [X] I have searched the issue tracker for a similar issue.
• [ ] If there is a stack dump, I have decoded it.
• [X] I have filled out all fields below.

Platform

• Hardware: [ESP-07]
• Core Version: [latest git hash or date]
• Development Env: [Arduino IDE]
• Operating System: [Windows]

Settings in IDE

• Module: [Nodemcu v1.0 (ESP12E Module) ]
• Flash Mode: [Not a Option]
• Flash Size: [4MB]
• lwip Variant: [v2 Lower Memory]
• Reset Method: [nodemcu]
• Flash Frequency: [Not a Option]
• CPU Frequency: [80Mhz]
• Upload Using: [SERIAL]
• Upload Speed: [115200] (serial upload only)

Problem Description

Nodemcu Serial.available(); function is not able to send total bytes available on serial it just send 1.

MCVE Sketch

#include "Arduino.h"

void setup()
{
    Serial.begin(9600);
}

String tmp = "";

void loop()
{
    while (Serial.available() > 0)
    {
        Serial.println("data in buffer : ");
        Serial.print(Serial.available());
        Serial.println("\n");
        tmp = Serial.readString();
    }

    if (tmp.length() > 4)
    {
        Serial.println("Data : " + tmp);
        Serial.println("Data length : " + String(tmp.length()));
        Serial.flush();
        tmp = "";
    }
}

Debug Messages

⸮R⸮⸮⸮⸮data in buffer : 
1

Data : hi hi hi

Data length : 10
⸮R⸮⸮⸮⸮R⸮⸮fgFj⸮data in buffer : 
1

Data : hihihih

Data length : 9

[mcspr]

function is not able to send total bytes available on serial it just send 1.

does exactly what you have asked, though? tmp = readString() replaces the whole string, perhaps you meant +=